Recycling method for the preparation and processing of a hydroxyl ammonium salt solution

Abstract

An improved process is described for the reduction of ammonium ions, while avoiding any increase in nitrate ion concentration, in a liquid stream recycled between a zone of synthesis of hydroxyl ammonium salt and a zone for synthesis of oxime, wherein the liquid stream is contacted with a gas stream consisting essentially of nitrogen monoxide and containing nitrogen dioxide at a pressure above 1 atmosphere, at a temperature of at least 80° C., such that after the contact the molar NO 2 /NO ratio of the gas stream is within the range of between about 10 -1 to 10 -4 :1.

We claim: 
     
       1. In a recycling method for the preparation and processing of a hydroxyl ammonium salt solution, in which an aqueous acid reaction medium is continuously recycled between a zone for the synthesis of hydroxyl ammonium salt and a zone for the synthesis of cyclohexanone oxime and in which nitrogen monoxide is added to the recycled liquid and catalytically reduced to hydroxyl amine by means of hydrogen, and the ammonium ions formed as a by-product in the reduction of the nitrogen monoxide are removed by contacting the recycling liquid containing ammonium ions with a gas flow substantially consisting of nitrogen monoxide and containing nitrogen dioxide to nitrogen, the improvement consisting essentially in that the recycling liquid is contacted with said gas flow containing nitrogen dioxide at a pressure of over 1 atmosphere, a temperature of from 85° to 165° C., and with the use of a gas flow which has a molar NO 2  /NO ratio measured after said contact that ranges between 10 -4  /1 and 10 -1  /1. 
     
     
       2. The recycling method according to claim 1 wherein said contact is effected with part of the recycling liquid in which the ammonium-ion concentration has been raised.